1. Field of the Invention
The present invention relates to an image recording method and apparatus for obtaining a visible image by performing thermal development after recording an image on a photothermographic imaging material by irradiating a laser beam to the photothermographic imaging material.
2. Description of Related Art
An image recording apparatus for forming an image on a film by heating the film so as to thermally develop it after forming a latent image by exposing a laser beam to the film of thermally developable silver halide photosensitive material on the basis of an image signal has been known (for example, cf. Japanese Patent Laid-Open Publication No. 2000-292893, Japanese Patent Laid-Open Publication No. 2000-292897 by the applicant or the like, or the like). In such an image recording apparatus, since thermal development treatment is performed, the density of the outputted image varies when the temperature in the inside of the apparatus varies. Therefore, it is difficult to obtain the density stably. In general, the temperature in the apparatus changes for about several xc2x0 C. to 10xc2x0 C. in accordance with the time course from power activation, change of environmental temperature, difference in number of sheets of the outputting images, or the like.
In order to stabilize the density by restraining the density variation of the outputted images that is caused by the temperature variation in the image recording apparatus in which thermal development treatment is performed, the following measures have been taken in earlier technology.
(1) Providing a density patch for controlling the density on the recording image beforehand, and measuring the density of the density patch portion after thermal development. Then, controlling the intensity of beam at the time of exposure so that the density will become a predetermined density at the time of outputting the image.
(2) Devising a ventilation system so that the temperature in the apparatus will be constant, and moreover, detecting the temperature in the apparatus and controlling the ventilation system.
(3) Controlling the intensity of beam irradiated to the film or the temperature of the thermal development drum on the basis of the detected temperature information in the apparatus.
The above-mentioned measures are attempted to restrain the density variation of the outputted image caused by the temperature variation. However, the control is complicated and the cost becomes high, so that it is difficult to obtain ability sufficient as density stability.
The present invention was made in view of the above-described problems in earlier technology. An object of the present invention is to provide an image recording method and apparatus that are capable of achieving density stability by restraining the density variation of the outputted image caused by a temperature variation.
In order to achieve the above-described object, according to an aspect of the present invention, the image recording method of the present invention comprises: forming a latent image on a photothermographic imaging material by exposing a light beam from a light source to the photothermographic imaging material; and forming a visible image on the photothermographic imaging material by thermally developing the photothermographic imaging material on which the latent image is formed; wherein a wavelength characteristic of the light beam from the light source is selected on a basis of a spectral sensitivity characteristic of the photothermographic imaging material so that a first sensitivity variation of at least one of the thermally developed photothermographic imaging material and the exposed photothermographic imaging material which is before being thermally developed, the first sensitivity variation being caused by a temperature variation, and a second sensitivity variation of the photothermographic imaging material according to a wavelength variation of the light beam from the light source caused by the temperature variation are offset.
According to the image recording method, the temperature of the light source varies while the sensitivity of the thermally developed photothermographic imaging material varies, according to the temperature variation. Thereby, the wavelength of the light beam exposed from the light source on the basis of an image signal varies, and the sensitivity of the photothermographic imaging material (the photothermographic imaging material in the forming of the latent image) varies. However, since the wavelength characteristic of the light beam is selected on the basis of the spectral sensitivity characteristic of the photothermographic imaging material, and the former sensitivity variation and the latter sensitivity variation are offset, the density variation of an outputted image caused by the temperature variation can be restrained and density stability can be achieved. Thus, in the image recording method according to the present invention, the variation in characteristic of development of the photothermographic imaging material according to the temperature and the spectral sensitivity characteristic of the photothermographic imaging material depending on the temperature characteristic of the wavelength of the light source are set so that both sensitivity variations will be offset. Thereby, the density variation of the outputted image caused by the temperature variation can be restrained effectively.
In the present specification, xe2x80x9coffsetxe2x80x9d means that two opposite effects obtained from two different characteristics weaken the mutual effects to some extent, respectively. It is not required to make mutual effects into zero. Further, to xe2x80x9cthermally developxe2x80x9d means to develop by heating the photothermographic imaging material on which the latent image is formed at a predetermined temperature for a predetermined time.
Further, according to a second aspect of the present invention, the image recording method of the present invention comprises: forming a latent image on a photothermographic imaging material by exposing a light beam from a light source to the photothermographic imaging material; and forming a visible image on the photothermographic imaging material by thermally developing the photothermographic imaging material on which the latent image is formed; wherein the light source has a temperature characteristic such that a peak of a wavelength of the light beam shifts to long wavelength side according to a temperature rise, and the light beam from the light source has the peak of the wavelength in a wavelength side longer than a peak of a spectral sensitivity of the photothermographic imaging material.
According to the image recording method, the sensitivity of the thermally developed photothermographic imaging material becomes large according to a temperature rise. On the other hand, the peak of wavelength of the light beam exposed from the light source on the basis of an image signal varies to the long wavelength side by the temperature rise of the light source according to the above-described temperature rise. Since the peak of the wavelength of the light beam is in the wavelength side longer than the peak of the spectral sensitivity of the photothermographic imaging material, the sensitivity of the photothermographic imaging material to the light beam varied to the long wavelength becomes small. Therefore, since the former sensitivity variation and the latter sensitivity variation of the thermally developable photosensitivity material are offset, the density variation of an outputted image caused by the temperature variation can be restrained, and density stability can be achieved.
Further, preferably, the photothermographic imaging material has a spectral sensitivity characteristic so that the spectral sensitivity of the photothermographic imaging material varies in a range of xe2x88x920.5% to xe2x88x923% to a variation of wavelength of 1 nm in a wavelength side longer than a peak of the spectral sensitivity. Thereby, the spectral sensitivity of the photothermographic imaging material may deteriorate moderately to the wavelength variation of the light source caused by the temperature variation.
Moreover, preferably, the above-mentioned image recording methods further comprise: measuring a density of a predetermined portion of the thermally developed photothermographic imaging material; and controlling at least one of the light source and the thermal development so that the measured density becomes a predetermined density. Further, the light source is preferably to be one of a semiconductor laser and a light emitting diode.
Further, according to a third aspect of the present invention, the image recording apparatus of the present invention comprises: an exposure portion having a light source, for forming a latent image on a photothermographic imaging material by exposing a light beam to the photothermographic imaging material from the light source; and a thermal development portion for forming a visible image on the photothermographic imaging material by thermally developing the photothermographic imaging material on which the latent image is formed; wherein a wavelength characteristic of the light beam from the light source is selected on a basis of a spectral sensitivity characteristic of the photothermographic imaging material so that a first sensitivity variation of at least one of the thermally developed photothermographic imaging material and the exposed photothermographic imaging material which is before being thermally developed, the first sensitivity variation being caused by a temperature variation in the apparatus, and a second sensitivity variation of the photothermographic imaging material according to a wavelength variation of the light beam from the light source caused by the temperature variation in the apparatus are offset.
According to the image recording apparatus, the temperature of the light source varies while the sensitivity of the photothermographic imaging material thermally developed in the thermal development portion varies, according to the temperature variation. Thereby, the wavelength of the light beam exposed from the light source on the basis of an image signal varies, and the sensitivity of the photothermographic imaging material (the photothermographic imaging material on which the latent image is formed) varies. However, since the wavelength characteristic of the light beam is selected on the basis of the spectral sensitivity characteristic of the photothermographic imaging material, and the former sensitivity variation and the latter sensitivity variation are offset, the density variation of an outputted image caused by the temperature variation can be restrained and density stability can be achieved. Thus, in the image recording apparatus according to the present invention, the variation in characteristic of development of the photothermographic imaging material according to the temperature and the spectral sensitivity characteristic of the photothermographic imaging material depending on the temperature characteristic of the wavelength of the light source are set so that both sensitivity variations will be offset. Thereby, the density variation of the outputted image caused by the temperature variation can be restrained effectively.
Further, according to a fourth aspect of the present invention, the image recording apparatus of the present invention comprises: an exposure portion having a light source, for forming a latent image on a photothermographic imaging material by exposing a light beam to the photothermographic imaging material from the light source; and a thermal development portion for forming a visible image on the photothermographic imaging material by thermally developing the photothermographic imaging material on which the latent image is formed; wherein the light source has a temperature characteristic such that a peak of a wavelength of the light beam shifts to long wavelength side according to a temperature rise in the apparatus, and the light beam from the light source has the peak of the wavelength in a wavelength side longer than a peak of a spectral sensitivity of the photothermographic imaging material.
According to the image recording apparatus, the sensitivity of the thermally developed photothermographic imaging material becomes large according to a temperature rise in the apparatus. On the other hand, the peak of wavelength of the light beam exposed from the light source on the basis of an image signal varies to the long wavelength side by the temperature rise of the light source according to the temperature rise in the apparatus. Since the peak of the wavelength of the light beam is in the wavelength side longer than the peak of the spectral sensitivity of the photothermographic imaging material, the sensitivity of the photothermographic imaging material to the light beam varied to the long wavelength becomes small. Therefore, since the former sensitivity variation and the latter sensitivity variation of the thermally developable photosensitivity material are offset, the density variation of the outputted image caused by the temperature variation can be restrained, and density stability can be achieved.
Further, the light source is preferable to be one of a semiconductor laser and a light emitting diode. Moreover, preferably, the photothermographic imaging material has a spectral sensitivity characteristic so that the spectral sensitivity of the photothermographic imaging material varies in a range of xe2x88x920.5% to xe2x88x923% to a variation of wavelength of 1 nm in a wavelength side longer than a peak of the spectral sensitivity.
Moreover, preferably, the above-mentioned image recording apparatuses further comprise: a densitometry portion for measuring a density of a predetermined portion of the photothermographic imaging material developed in the thermal development portion, wherein at least one of the exposure portion and the thermal development portion is controlled so that the density measured by the densitometry portion becomes a predetermined density. Thereby, the density variation of the outputted image caused by the temperature variation can be corrected and restrained in further high accuracy.